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The Resistance Effect of Lignin on Hemicelluloses Removal During Bamboo Hydrothermal Prehydrolysis |
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DOI:10.11980/j.issn.0254-508X.2019.06.001 |
Key Words:bamboo prehydrolysis hemicelluloses removal lignin pore structure |
Fund Project:国家自然科学基金项目(31500488、31770632)。 |
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Abstract:Prehydrolysis is one of the most important steps for dissolving pulp production with an objective of degradation and dissolution of hemicelluloses, but the hemicelluloses removal can only reach to a limit level. In this work, the influence of lignin on the hemicellulose removal especially in the later stage of prehydrolysis was evaluated by the analysis of the relations between lignin and hemicellulose removal. The changes of pore structure of the bamboo powder which was prepared by grinding the bamboo chips and used to implement prehydrolysis simulation, the surface morphology of the bamboo chips, and together with lignin migration were used for elucidating the lignin resistance effect on hemicellulose removal. The results showed that hemicelluloses removal was closely correlated with lignin, both lignin and hemicellulose were degraded and dissolved at the same time in the initial stage of prehydrolysis, most of the hemicelluloses removed when the lignin removal reached to the maximum. As prehydrolysis continued the hemicelluloses removal no longer increased when lignin removal decreased sharply. It was referred from ESEM analysis that extensive pretreatment made the surface of fiber full of hydrophobic lignin coating which hindered the water attack and the diffusion of degradation products. The results from bamboo powder simulation experiment also confirmed that the pore volume and pore diameter of bamboo powder decreased obviously at the later stage of prehydrolysis. The relative high lignin content and the change of microstructure of the fiber caused by lignin migration were the main reasons for hindering hemicelluloses further removal. |
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